tests: avoid cryptic nodeids in tests/test-rename-merge1.t

These two nodeids had not been part of any output before, so one can't
know which revision they refer to without adding something like `hg
log` before them. It turned out that '.^' was equivalent for both of
them, so that's what I replaced them with.

Differential Revision: https://phab.mercurial-scm.org/D6280

tests/test-rename-merge1.t

@@ -75,7 +75,7 b' This used to trigger a "divergent rename'
   $ hg cp b b3
   $ hg cp b b4
   $ hg ci -A -m 'copy b twice'
-  $ hg up eb92d88a9712
+  $ hg up '.^'
   0 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ hg up
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
@@ -87,7 +87,7 b" We'd rather not warn on divergent rename"
   $ hg cp b b3
   $ hg mv b b4
   $ hg ci -A -m 'divergent renames in same changeset'
-  $ hg up c761c6948de0
+  $ hg up '.^'
   1 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ hg up
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved